Delayed ischemic neurological deficits are associated with subarachnoid aneurysmal hemorrhage and vasospasm. Identifying proteins that predict the occurrence of these events may improve outcomes through earlier recognition and treatment of vasospasm. We have evaluated 65 patients who have developed subarachnoid hemorrhage and were enrolled an IRB-approved study at Johns Hopkins University. Their blood has been screened with methods to identify candidate proteins using multiplex arrays and high density antibody based arrays. Thirty potential markers have been identified that are differentially expressed in patients with subarachnoid hemorrhage. Some of these markers are only present at the time of hospital admission and may be associated with the subsequent development of vasospasm. Similarly, we have identified some proteins that are only present in patients who do not develop vasospasm. We are confirming these initial studies that are semiquantitive with additional quantative to validate the initial observations. In addition, we are enlisting additional patients to confirm the original observations.